The present invention relates to a tensioning system for a mobile telescopic crane, in which the telescopic mast is outwardly braced via a tensioning means. In particular, the present invention relates generally to optimally integrating a tensioning system and the components connected to it with a jib design on the superstructure of a mobile telescopic crane.
The aim of any jib design is to keep the ratio of its tare weight to its working load small. The overall system must also exhibit sufficient rigidity to meet the performance capability demanded by the standards.
Jib construction mainly employs fine-grained constructional steel with increasingly higher strengths up to a yield point of 1100 N/mm2. The modulus of elasticity and the available design space remain almost unchanged, hence the deformations border on the limits of performance capability. Deformations such as in a fishing rod are, however, not desirable in lifting platforms and in the field of cranes.
The hollow sections used for a jib are mainly subjected to bending stresses. In terms of tension, only the peripheral fibres are utilised, the material being inactive in the centre. The stability of other panel-like areas is endangered; using superior material has no effect.
It is important to develop light-gauge designs which optimally utilise the material strengths; this applies in particular to vehicle cranes. Filigrees and meticulous designs with little deformation are efficient and save weight. The bearing loads in the range of strength and in the range of steadiness of the existing crane classes would have to be significantly increased still.
A jib section for a braced system with high-tensile materials is described in DE 201 20 121 U1. This teaches how an increase in bearing load can be achieved by shell-segment designs curved outwards. Bracing designs are known from DE 200 02 179 U1 and DE 100 22 658 A1 which are limited to an overhead line of the main jib, arranged in the level luffing plane or inclined with respect to the level luffing plane, wherein a rigid or linearly adjustable mast is fastened to the jib base portion.
It is the object of the present invention to provide a tensioning system for a mobile crane telescopic jib, said system improving the bearing capacity of the telescopic mast, wherein mast deformations in particular are to be reduced.